Variable inductor and method for adjusting inductance of same

Abstract

A variable inductor includes an insulating substrate ( 1 ), a thermally softenable spiral coil ( 2 ) provided on the insulating substrate ( 1 ), and a pair of input/output terminals ( 3, 4 ) each connected electrically to a respective end of the coil ( 2 ). Preferably, the coil ( 2 ) is made from a non-crystalline thin film metallic glass which softens in a supercooled liquid phase.

The invention claimed is: 
     
       1. A variable inductor comprising: a substrate; a thermally softenable spiral coil provided on said substrate and including two ends fixed to said substrate; and a pair of input/output terminals electrically connected to said ends of said coil, respectively;
 wherein said coil is made from a non-crystalline thin film metallic glass which softens in a supercooled liquid phase; and 
 wherein a portion of said coil other than said two ends is separated from said substrate for floating. 
 
     
     
       2. The variable inductor according to  claim 1 , wherein said coil is formed from at least one material selected from a group consisting of an electrically conductive material, a non-conductive material formed with a coating of electrically conductive material, and an electrically conductive material formed with a coating of another electrically conductive material. 
     
     
       3. The variable inductor according to  claim 1 , wherein a piezoelectric thin film and a driving electrode are formed over said coil, and a connection terminal connected to said drive electrode is provided on said insulating substrate. 
     
     
       4. The variable inductor according to  claim 1 , further comprising a pressing member abutting against said coil, and an actuator or adjustment mechanism for driving the pressing member heightwise of said coil. 
     
     
       5. The variable inductor according to  claim 4 , wherein said actuator supports said pressing member from an opposite side to said coil. 
     
     
       6. The variable inductor according to  claim 4 , wherein said actuator supports said pressing member from a same side as said coil. 
     
     
       7. The variable inductor according to  claim 1 , wherein a drive electrode is further provided on said substrate underneath said coil, via an insulating layer, in such a manner that a height of said coil can be changed electrostatically by applying a voltage between the drive electrode and said coil. 
     
     
       8. The variable inductor according to  claim 7 , wherein a plurality of said drive electrodes are provided opposing said coil, and connection terminals are provided for applying voltage individually to each of the drive electrodes. 
     
     
       9. The variable inductor according to  claim 7 , wherein said drive electrode comprises a spiral slit extending circumferentially of said coil. 
     
     
       10. The variable inductor according to  claim 7 , wherein said drive electrode is spiral and has a width which varies as the electrode extends circumferentially of said coil. 
     
     
       11. The variable inductor according to  claim 7 , further comprising a connection plate connected to one end of said coil, for contacting a portion of said coil other than said end, thereby reducing the effective number of windings of said coil, when the coil has been deformed elastically in a height reducing direction, and for conversely increasing the effective number of windings of said coil when said coil has been deformed elastically in a height increasing direction. 
     
     
       12. The variable inductor according to  claim 11 , wherein said connection plate has a doughnut shape. 
     
     
       13. The variable inductor according to  claim 12 , wherein said connection plate is provided with a plurality of slits arranged at circumferential intervals. 
     
     
       14. A method for adjusting the inductance of a variable inductor comprising an insulating substrate, a thermally softenable spiral coil provided on said insulating substrate and including two ends fixed to said substrate, and a pair of input/output terminals electrically connected to said ends of said coil, respectively, a portion of said coil other than said two ends being separated from said substrate for floating, said method comprising, at the least, the steps of:
 compressing or extending said floating portion of said coil, thereby changing a height thereof; and 
 heating said coil to a softening temperature thereof after the change of the height followed by cooling to set an initial height of said coil. 
 
     
     
       15. The method for adjusting inductance according to  claim 14 , further comprising the step of fixing the initial height set for said coil by enclosing said coil in resin. 
     
     
       16. The method for adjusting inductance according to  claim 14 , further comprising the step of dynamically changing the height of said coil by compressing or extending said coil electrostatically or piezoelectrically after the setting of the initial height. 
     
     
       17. The method for adjusting inductance according to  claim 14 , wherein said coil is made from a non-crystalline thin film metallic glass which softens in a supercooled liquid phase.